Manufacture of polyketones

ABSTRACT

Polyketones are manufactured by reacting an aromatic carboxylic acid with a biractive aromatic compound, using as a catalyst a combination of a carboxylic acid anhydride and phosphoric acid, or equivalent thereof. The product polymers are useful as molding resins.

This application claims the benefit of provisional application No.60/122/316, filed Mar. 1, 1999.

FIELD OF THE INVENTION

Polyketones are manufactured by the phosphoric acid/carboxylic acidanhydride catalyzed reaction of a dicarboxylic acid with an electronrich aromatic compound which behaves as a difunctional compound.

TECHNICAL BACKGROUND

Polyketones, especially aromatic polyketones, are important engineeringpolymers, often having the advantages of chemical resistance, good hightemperature properties, good tensile properties, and others. Typicalengineering polyketones are poly(etheretherketone) (PEEK) (I), andpoly(etherketone) (PEK) ((II), having the repeat units

Most commonly these polymers have been made by the condensation of anaromatic hydroxy compound with an aromatic fluoride. For example, PEEKmay be made by the reaction of 4,4′-difluorobenzophenone with thedianion of hydroquinone, while PEK may be made by the reaction of4,4′-difluorobenzophenone with the dianion of4,4′-dihydroxybenzophenone, or the base promoted self condensation of4-fluoro-4′-hydroxybenzophenone. While these reactions suffice to makethe desired polymers, they have serious disadvantages. The benzophenonemonomers required are expensive, and the reactions produce byproductssuch as inorganic fluorides which must be properly disposed of

Another method of making aromatic ketones is the Friedel-Craftssynthesis. While this may employ somewhat cheaper ingredients thereaction is often more difficult to run and unwanted byproducts areproduced. For example at least stoichiometric quantities of a Lewis acidsuch as aluminum chloride must be used, which later must be separatedfrom the polymer and discarded or otherwise used. Therefore improvedmethods of making polyketones are desired.

T. P. Smyth et al. J. Org. Chem, vol. 63, p. 8946-8951 (1998) describe areaction for forming aromatic ketones reacting a carboxylic acid with anaromatic compound using as an activation system, a combination ofphosphoric acid and trifluoroacetic anhydride. No mention is made ofusing such a reaction to form polymers.

U.S. Pat. No. 4,861,856 discloses a process for preparing polyketonesand poly (ketone -sulfone) polymers, whereby reactive aromatic compoundsare contacted with aromatic dicarboxylic acids in the presence oftrifluoroacetic anhydride and phosphorous pentoxide. U.S. Pat. No.4,839,459 discloses a pros for preparing poly(ether-ketone) polymers.

EP A 229 470 to co-poly ketones, process for making them and process forblending them with other polymers.

SUMMARY OF THE INVENTION

This invention concerns, a process for the production of polyketones,comprising contacting an aromatic compound which is bireactive, adicarboxylic acid, phosphoric acid, and a carboxylic acid anhydride.

DETAILS OF THE INVENTION

By hydrocarbyl herein is meant a univalent radical containing carbon andhydrogen while substituted hydrocarbyl means hydrocarbyl substitutedwith one or more functional groups including complete replacement of thehydrogens). By hydrocarbylene is meant a divalent group containing onlycarbons and hydrogen containing two free valences to different carbonatoms by hydrocarbylene is meant a group containing carbon and hydrogenwith to free valences to the same carbon atoms, each of these valencesbound to a different atom. By substituted hydrocarbylene is meant ahydrocarbylene group substituted with one or more function groups, andin which all of the hydrogen may be replaced.

By a “bireactive” compound herein is meant a compound, such as anaromatic compound, in which substantially all molecules of that compoundwill each react twice in the ketone forming polymerization process.Since normally the “reactive group” in such a compound is a hydrogenbound to a carbon atom, which is not usually thought of as a functionalgroup, this term is used.

By an “aromatic compound which is bireactive” is meant a compound whichcontains at least one aromatic ring which is bireactive. This compoundmay contain more than one aromatic ring. If more than one aromatic ringis present it may be fused ring system such as found in naphthalene oranthracene a ring system connected directly by a covalent bond, such asis found in biphenyl, or a ring system connected through another group,such as is found in diphenyl ether, diphenylmethane, and2,2-diphenylpropane. Other groups may be present

on the aromatic rings so long as do not interfere with the ketoneforming polymerization reaction. It is preferred that the aromatic ringsare carbocyclic rings. It is also preferred that the aromatic ring orrings of this compound are naphthyl ring systems or phenyl ring(s), morepreferably phenyl rings. More than one aromatic compound which isbireactive may be present to form a copolymer.

T. P. Smyth, et al. postulate that the ketone forming reaction is anelectrophilic attack on an aromatic ring of the bireactive compound. Itis well known in the art that in such electrophilic reactions asubstrate, such as the bireactive compound, is more reactive the more“electron-rich” it is. Aromatic rings can be made more electron rich byhaving electron donating substituents attached to these rings. Suchsubstituents include groups such as ether, alkyl, and tertiary amino,and are well known in the art. The presence of such groups will tend tomake the bireactive compounds more reactive and ensure that it is infact bireactive instead of monoreactive. Useful compounds for thebireactive compound include naphthalene, methylnaphthalene,methoxynaphthalene, benzyl ether, stilbene, diphenyl carbonate, benzylphenyl ether, biphenyl, terphenyl, fluorene, and a compound of theformula

wherein R¹ is —O— (diphenyl ether), alkylidene (for example —CH₂—,—CH₂CH₂—, or (CH₃)₂C<), and R³ is hydrocarbylene, substitutedhydrocarbylene or hydrocarbylidene, more preferably alkylene oralkylidene. Preferred bifunctional compounds are (III), especially when(III) is diphenyl ether. Useful groups for R³ include 1,2-ethylene,1,3-phenylene and 1,4-phenylene. More than one bireactive aromaticcompound may be present to give a copolyketone.

Any carboxylic acid anhydride may be used. Carboxylic acid anhydridehere has the usual meaning, a compound of the formula R²C(O)O(O)CR²wherein each R² is independently hydrocarbyl or substituted hydrocarbyl.It is preferred that both of R² are the same. It is preferred thatHammett σ_(m) for each of R² is about 0.2 or more, more preferably 0.4or more. Hammett σ_(m) constants are well known in the art, see forinstance C. Hansch, et al., Chem. Rev., vol. 91, p. 185ff (1991).Preferred groups for R² are perfluoroalkyl, and perfluoromethyl isespecially preferred.

The dicarboxylic acid may be any organic dicarboxylic acid, and maycontain other groups which do not interfere with the ketone formingreaction. Useful dicarboxylic acids include terephthalic acid,isophthalic acid, 4,4′-bibenzoic acid, 2-methylterephthalic acid,2,6-naphthalene dicarboxylic acid, 2-chloroterephthalic acid,bis(4,4′-dicarboxyphenyl)ether, cyclohexane-dicarboxylic acid,norbornanedicarboxylic acid, 2,5-pyridinedicarboxylic acid, and2,6-pyridinedicarboxylic acid. Preferred carboxylic acids are aromaticdicarboxylic acids, that is compounds in which the carboxyl groups arebound directly to aromatic rings. Preferred aromatic dicarboxylic acidare terephthalic acid, isophthalic acid, 4,4-bibenzoic acid and2,6-napththalene dicarboxylic acid, and terephthalic acid andisophthalic acid are especially preferred. More than one dicarboxylicacid may be present in the process to give a copolyketone.

The molar ratio of the aromatic compound which is bireactive todicarboxylic acid should preferably be about 1:1, especially preferablyabout 1.0:1.0, and more preferably 1.00:1.00, to achieve highermolecular weight polymer. This is normal for most condensationpolymerizations to achieve higher molecular weight polymer. The molarratio of carboxylic acid anhydride to dicarboxylic acid is preferablyabout 0.1 to about 20, more preferably about 2 to about 4. The molarratio of phosphoric acid to dicarboxylic acid is preferably about 0.01to about 2.0, more preferably about 0.05 to about 1.0.

The pressure at which the process is run is not critical, autogenous(for processes in which the boiling point of one or more of thereactants is exceeded) or atmospheric pressure being useful. In order toprevent unwanted side reactions such as hydrolysis of the carboxylicacid anhydride by atmospheric moisture, it is convenient to run thereaction under an inert atmosphere, such as nitrogen. The process may beagitated. A useful reaction temperature range is about 0° C. to about300° C., preferably about 25° C. to about 250° C, more preferably about30° C. to about 200° C.

The reaction may be run neat, i.e., without other added liquids orsolids. It may also be run in the presence of another liquid. Thisliquid, which should be inert under reaction conditions, may be asolvent for one or more of the starting materials and/or productpolymer, but one or more of the process ingredients may simply besuspended in the liquid. Suitable liquids includes alkanes such asoctane, electron deficient aromatic compounds such as o-dichlorobenzene,and halogenated alkanes such as 1,2-dichloroethane. The process may berun as a batch, semi-batch or continuous reaction. For example acontinuous reaction may be run in a continuous stirred tank reactor or apipeline-type reactor. Such reaction systems are well known in the art.

Aromatic compounds that are trireactive or higher, or tri- or highercarboxylic acids may also be present in the process in small amounts (toproduce a thermoplastic). Addition of these “polyfunctional” compoundswill give branching, which may be desirable in the polymer for polymerprocessing reasons. However too much of these polyfunctional compoundswill lead to crosslinking. Crosslinking is undesirable for making linearor branched (melt or solution processible) polymer, but may be desiredis a thermoset resin is the desired product.

Included within the meaning of the ingredients added to this process areany combinations of (other) ingredients which are known to react to givethe needed ingredients in situ.

The polymers produced by the process are useful as molding resins forvarious types of parts, such as parts that are heat and/or chemicallyresistant.

Model Example 1

To a 50 mL Schlenk flask equipped with a nitrogen inlet was added 4.0 g4-benzoylbenzoic acid (17.7 mmol) followed by 7.43 g trifluoroaceticanhydride (35.4 mmol). The mixture was cooled to 0° C. using an externalwet ice bath and 0.204 g of 85% phosphoric acid (1.77 mmol) solution wasadded. After allowing to stir for 30 min, 2.10 g anisole (19.4 mmol) wasadded. The solution was allowed to warm to room temperature and stir foran additional 30 min after which time the temperature was raised to 60°C. The mixture was allowed to stir for 4 h at 60° C. After allowing tocool to room temperature, the solution was diluted with chloroform,washed twice with 10% sodium carbonate (aq.) solution and once withwater. The organic solution was dried (MgSO₄) and the solvent wasremoved under reduced pressure to afford an off-white solid, which was amixture of 80% 4-(4-methoxybenzoyl)benzophenone and 20%4-(2-methoxybenzoyl)-benzophenone, as determined by ¹H NMR.

Model Example 2

To a 100 mL Schlenk flask was added 2.0 g (12.0 mmol) isophthalic acidfollowed by 10.1 g (48.1 mmol) trifluoroacetic anhydride. The mixturewas cooled to 0° C. and 2.80 g (24.3 mmol) of 85% phosphoric acidsolution was added. The mixture was allowed to stir for 30 min at roomtemperature before 2.86 g (26.4 mmol) of anisole was added. Afterstirring for 30 min at room temperature the reaction was heated at 65°C. for 4 hours. After cooling to room temperature the reaction wasdiluted with 150 mL chloroform and washed with 3×50 mL of 2% aqueoussodium carbonate and then 50 mL water. After drying (MgSO₄), the solventwas removed by rotary evaporation to provide an amber oil. High PressureLiquid Chromatographic analysis showed that 35% of the product was theortho, para isomer, while 65% of the product was the para, para isomer.

EXAMPLE 1

To a 100 mL Schlenk flask was added 2.0 g (12.0 mmol) isophthalic acid,2.579 g (12.0 mmol) 1,2-diphenoxyethane, 20.3 g (96.7 mmol)trifluoroacetic anhydride, followed by 10 mL o-dichlorobenzene.Phosphoric acid (2.78 g, 24.1 mmol, 85 wt. % solution) was then addedvia syringe. The mixture was stirred for 1 hour at room temperature andthen the temperature was raised to 65° C. The mixture was heated for 8 hat 65° C. and was then cooled back to room temperature. After stirringfor 12 h at room temperature the polymer was precipitated into stirringmethanol. The polymer was filtered, collected, and stirred in a 1%sodium carbonate solution for 2 h. The colorless polymer was thenrefiltered and washed with water and methanol. Analysis of the polymerby Matrix Assisted Laser Desorption Mass Spectrum showed a molecularweight range of 1000-5000 g/mol, with the most intense signal appearingat 1761 g/mol.

What is claimed is:
 1. A process for the production of polketones,comprising, contacting an aromatic compound that reacts twice in theketone forming polymerization process, dicarboxylic acid, phosphoricacid, and a carboxylic acid is an wherein a molar ratio of phosphoricacid to dicarboxylic acids is 0.01 to 2.0.
 2. The process as recited inclaim 1 wherein said dicarboxylic acid is an aromatic dicarboxylic acid.3. The process as recited as claim 2 wherein said carboxylic anhydrideas the formula R²C(O)O(O)CR², wherein each R² is independentlyhydrocarbyl or substituted hydrocarbyl wherein one, some, or allhydrogen atoms are replaced by functional groups, and each R² has σ_(m)(Hammett constant) of 0.2 or more.
 4. The process as recited in claim 3wherein said m (Hammett constant) is 0.4 or more.
 5. The process asrecited in claim 3 wherein each R² is independently perfluoroalkyl. 6.The process as recited in claim 2 wherein said aromatic dicarboxylicacid is terephthalic acid or isophthalic acid.
 7. The process as recitedin claim 2 wherein said aromatic dicarboxylic acid is terephthalic acid,isophthalic acid, 4,4′-bibenzoic acid or 2,6-naphthalene dicarboxylicacid.
 8. The process as recited in claim 1, 4 or 6 wherein said aromaticcompound is naphthalene, methylnaphthalene, methoxynaphthalene, benzylether, stilbene, diphenyl carbonate, benzyl phenyl ether, biphenyl,terphenyl, fluorene, and a compound of the formula

wherein R¹ is —O—(diphenyl ether), alkylidene (for example —CH2—CH₂CH₂—,or (CH₃)₂C<), and R³ is hydrocarbylene, substituted hydrocarbylene orhydrocarbylidene.
 9. The process as recited as claim 1, 5 or 6 whereinsaid aromatic compound is diphenyl ether.
 10. The process as recited inclaim 2 which is run at a temperature of 0° C. to 300° C.
 11. Theprocess as recited in claim 2, 5, 6 or 8 which is run at a temperatureof 30° C. to 200° C.
 12. The process as recited in claim 2, 5, 6, 8 or11 wherein a molar ratio of aromatic compound to dicarboxylic acid is1.00:1.00.
 13. The process as recited in claim 1 which is run neat. 14.The process as recited in claim 1 which is run in the presence of anadditional liquid.
 15. The process as recited in claim 1 wherein assmall amount of aromatic compound which is trireactive or higher and/ortri- or higher carboxylic acid is also present to cause branching of thepolyketone.
 16. The process as recited in claim 2, 5, 6, 8, 11 or 12wherein a molar ratio of carboxylic acid anhydride to dicarboxylic acidis 0.1 to
 20. 17. The process as recited in claim 16 wherein said molarratio of carboxylic acid anhydride to dicarboxylic acid is 2 to
 4. 18.The process as recited in claim 1 wherein said molar ratio of phosphoricacid to dicarboxylic acid is 0.5 to 1.0.